Hi,
I'm new to the forum and I need some help.
I feel I need to give some detail, so this is pretty long.

I have a 1997 K1500 Suburban with 120,000 miles. We bought it in the fall of 2012 for about $3k.
My wife wanted something other than my 1975 K25 GMC PU to ride in while towing our boat ( a 24' pontoon).

On May 16th 2013 I was towing the boat back from the water and it overheated.
The engine started rattling and lost power very rapidly.
When I got the hood open the radiator cap was popped off and it was steaming very hard.

We let it cool and put some water in it, I started engine to add some more water and it came back out like a geyser.
I shut it off , topped the coolant off and limped the rest of the way home, about 4 miles.
When I got home the reservoir was full of coolant and there was a distinct gurgling sound.

The next day I replaced the thermostat and radiator cap.
After a little warm up coolant started backup into the reservoir and there was white smoke coming out the tail pipe.
Definitely a blown head gasket or cracked head or both.

The engine had other issues and a entire engine replacement looked like our best path.

Due to some personal time constraints I contacted a local repair shop to install it.
They agreed upon 16 hours of labor to replace the engine.
They purchased the engine so they would be the warranty point.
I went with the 12530283 L31 5.7 4 bolt main HD GM engine.

I also added a Delphi spider to replace the poppets (FJ10566 Fuel Injector SCPI to MFI Conversion Assembly $264 @amazon) and Flo tech ceramic coated shorty headers (Jegs).
I provided a Felpro gasket set, Iridium plugs, 7.5 mm plug wires, ARP bolts for the intake, full set of Bosch O2 sensors, a water pump and all the fluids.
I even provided 4 gallons of distilled water and a magnetic oil drain plug.
They said they would let me know about the Distributor cap and rotor, we ended replacing them.

I dropped off the ailing suburban on May29th.
They replaced the engine pretty quickly.
Well then they had some problems getting it running right. They were off one tooth on the distributor.

Then it still ran poorly.
They said they were 99% sure the catalytic converter was plugged.
I asked if they had a test pipe they could install before I drop $350 for a Cat.
I got a test pipe installed for $285 and it still ran bad.
They brought it to a custom programmer and made some changes on the Torque management and disabled the rear O2 sensor.
The Tech said that #1 & #3 were miss firing - the local tech said #2 plug looked like it had a manufacturing defect.
I installed the new distributor and rotor and plug. It ran much better.
It still gave a service engine light (MIL) (yes I did clear it by disconnecting the battery).
I cleaned the MAF and cleared the MIL. It stayed out about 24 hours and put on about 100 miles of city driving.

The next morning (Sunday) I tried to use it and got MIL and very poor performance about 2 miles out from home.
I was getting code for P0131 and P0151 , both forward O2 Sensors.
The MIL cleared on the way to their shop the next morning.
They said drive it and come back when it's on (MIL).
I drove it about 2 miles and got another MIL.
Turn around and go back.
I got it back 2 days later with the old O2 sensors installed.
I got about 12 miles and got another MIL.
I drove back to their shop.
Knock sensor...

Got it back drove it and got MIL again.
P0131 and P0151 again.
After 2 days I was told the fuel pressure is a bit low- replace the pump with a Walbro GCA758-2 255 lph pump.
The sending unit was also replaced. (It was a good thing, as the old one was on it's 2nd pump and the connector was melted)

I got it back, changed the oil and test drove it and got another MIL.

I admit I drive it like I stole it to get the MIL's but it's a brand new engine.

I got back to home and thought for a while.
I began to wonder what kind of tests I could make.
I grabbed my laser temp reader, a piece of paper and pen and headed out.

I ran the suburban about 5 miles.
It was fully warmed up and I pulled over and measured and recorded the temperatures of the header pipes.
This is what I found:
8 - 291 7 - 321
6 - 259 5 - 290
4 - 269 3 - 289
2 - 204 1 - 332

I drove easy to the House and when I got home I let it idle for a while then took them again

8 - 383 7 - 461
6 - 332 5 - 325
4 - 289 3 - 323
2 - 227 1 - 380

#2 appears a lot cooler than the others,
#7 looks hotter than the others.

Does this mean anything to anyone?

I am thinking the following things:

1. An injector has a kink in a line.
2. An injector has not been pushed all the way in.
3. The Delphi injector rig is bad.
4. #1 & #2 will cost the repair shop money, #3 will cost me money.
6. Maybe some one here can help with an idea or 2.


If anyone has some words of advice I sure could use them.

Thanks,

Mike Woj
Interlachen, Florida